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12-29-2012, 04:00 PM
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Join Date: Dec 2010
Location: SLC UT
Posts: 68
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Ugly Fuel Tank Screw Countersink on main spar
Using the Vans method of #30 Countersink using a platenut as a guide, it sure didn't come out too pretty:
Pretty disappointed as from here on the mistakes start getting expensive! Anticipating me screwing this up, I only riveted one platenut on to try this method. Did about 5 hours of research about this hole prior to cutting it- High anxiety!
Since this is just a hole for a dimple, should I switch to the other method (backing bar w rivets and #30 guide hole) or do the hole just come out like this sometimes?
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12-29-2012, 04:12 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Dave it does happen some times, but technique is a big factor.
Do not use an air drill.
Do not turn the cutter fast.
Use a good cordless drill with good torque.
Make sure the countersink cage is set up properly by testing on scrap and to practice your technique.
Use a lot of pressure and slow speed (not ultra slow... you will learn with practice). If the drill has selectable speeds, use one of the slower ranges so that you can run the motor at full.
The slower speed with a lot of pressure will minimize the likelihood of cutter chatter.
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12-29-2012, 04:20 PM
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Join Date: Oct 2005
Posts: 1,516
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Everything Scott said.
I found the single flute countersink tools from Clevland Tools very helpful for some applications, especially the ones you are working on.
http://www.cleavelandtool.com/prodinfo.asp?number=CCSF
__________________
Ernst Freitag
RV-8 finished (sold)
RV-10 Flyer 600 plus hours
Running on E10 mogas
Don't believe everything you know.
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12-29-2012, 04:22 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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A one-hole countersink cutter would help here, again at a low speed...
http://www.aircraft-tool.com/shop/de...UCT_ID=4100-30

__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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12-29-2012, 04:32 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,686
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And don't forget the Boelube.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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12-29-2012, 04:44 PM
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Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,778
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Heck with the nutplate method... grab a piece of .060 or heck even 1/8" bar stock and drill it up with the correct drill size. Use the rivet holes for a neighboring nutplate to drill and cleco the piece on the back side and then Countersink the spar. You will have a few different patterns... Check and set the plate up for each hole. The countersink will be clean and smooth... oh and very hard to make the countersink chatter. You will be extremely pleased. 
__________________
Reiley
Retired N622DR - Serial #V7A1467
VAF# 671
Repeat Offender / Race 007
Friend of the RV-1
Last edited by LifeofReiley : 12-29-2012 at 04:53 PM.
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12-29-2012, 04:50 PM
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Join Date: Nov 2010
Location: West Linn, Oregon
Posts: 1,351
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What Riley said. A good thick piece of metal on the back side to hole the guide in the countersink will prevent this from happening. If you look at the hole in your countersink, the hole is enlarged so nothing holds the guide point anymore.
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CharlieWaffles - But you can call me " Mark"
RV-10
N928MT
Flying - AKA Still Tinkering
Build Project Site
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12-29-2012, 05:10 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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As always, there are a lot of different ways to complete a process... some take a lot more time and effort than the one described in the manual, which does work well, if the proper technique is used (and some lubricant that I forgot to mention... thanks Walt).
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12-29-2012, 05:50 PM
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Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,778
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Quote:
Originally Posted by CharlieWaffles
What Riley said. A good thick piece of metal on the back side to hole the guide in the countersink will prevent this from happening. If you look at the hole in your countersink, the hole is enlarged so nothing holds the guide point anymore.
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Mark is correct, using the nutplate method your nice facory hole will end up way oversized. For me it is all about quality and sometimes it can take a little more time but the end product is well worth it. 
__________________
Reiley
Retired N622DR - Serial #V7A1467
VAF# 671
Repeat Offender / Race 007
Friend of the RV-1
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12-29-2012, 06:13 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by LifeofReiley
Mark is correct, using the nutplate method your nice facory hole will end up way oversized. For me it is all about quality and sometimes it can take a little more time but the end product is well worth it. 
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I disagree...
I have at least 10 sets of wings using the described method (install the nut plate first, and use the proper size pilot, and turn it slow).
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